1. Field of the Invention
Embodiments of the present invention generally relate to image processing. More particularly, embodiments of the present invention relate to aligning page images.
2. Related Art
Information automation has enabled increased productivity by converting paper-based pages to an electronic page image format. This allows automated page delivery, page sorting, page preservation, and other applications. Image processing facilitates this information automation.
Once a paper-based page is scanned to generate the page image, a number of processes can be performed on the page image. Rather than having encoded information such that characters and words are a sequence of digital bits, the page image is comprised of a plurality of pixels. Hence, search and identification of page images is more complex.
To facilitate search and identification of page images, a bar code is sometimes included in the paper-based page. However, this technique can be costly and inconvenient. Others have included unique characteristic features to the paper-based page to facilitate search and identification of page images. Again, this scheme can be inconvenient and limited to a few applications.
Typically, comparison techniques are utilized to identify page images. One method of comparing page images is cross-correlation, which is usually performed by first two-dimensionally Fourier transforming the page images to be compared. Then, the pixels are multiplied point by point. Finally, the page images are inversely transformed back into a spatial representation to show correlation peaks.
To improve the results of any comparison technique, the page images to be compared are aligned first. A Fourier method or a simple image cross-correlation is usually used to align the page images. However, this can be computationally intensive and time consuming.
Therefore, the typical prior art alignment schemes are all problematic and suffer different drawbacks.